At present, the broadband access technology comes in two types: copper wire access technology such as digital subscriber line (xDSL) technology and optical access technology. An access network based on the optical access technology is called an optical access network (OAN).
The PON technology is an optical access technology for point-to-multipoint transfer. FIG. 1 shows a PON system. A PON system includes an optical line terminal (OLT), an optical distribution network (ODN), and an optical network unit (ONU). The OLT provides a service node interface (SNI) for the OAN, and is connected to one or more ODNs. An ODN is a passive optical splitting component, which transmits the downstream data of the OLT to each ONU through optical splitting. Likewise, the ODN transmits the upstream data of the ONU to the OLT through convergence. The ONU provides a user network interface (UNI) for the OAN, and is connected to the ODN. If the ONU also provides the user port function, for example, Ethernet user port or plain old telephone service (POTS) user port, the ONU is called an “ONT”. Unless otherwise specified, ONU and ONT are collectively called “ONT” hereinafter.
In the general PON access technology, the downstream traffic of the OLT is broadcast to each ONT through time division multiplexing (TDM), and each ONT receives the traffic as required; the upstream traffic of the ONT is controlled through the OLT, so that only a specific ONT is allowed to transmit data at a time and the data is transmitted to the OLT through time division multiple access (TDMA).
The ITU-T has established the broadband passive optical network (BPON) standard and the gigabit passive optical network (GPON) standard. The OLT configuration and ONT management modes are defined in the BPON and GPON standards. The OLT manages the ONT through an ONU management and control interface (OMCI) path. An OMCI is a configuration transmission path defined in the BPON and GPON standards. It is set up by the ONT between the OLT and the ONT when the ONT is registered at the OLT. The OMCI is a master-slave management protocol, in which the OLT is a master device and the ONT is a slave device. Through an OMCI path, the OLT controls multiple ONIs connected under it.
In the OMCI protocol, the ONT data managed by the OLT is abstracted into an independent management information base (MIB). A basic unit of the MIB is management entity (ME). According to the function configuration of the ONT, multiple MEs of the ONT are controlled by the OLT through an OMCI, as defined by the BPON and GPON standards. Under the control of the OLT, the ONT implements the configuration and management of all the MEs.
A network device generally has more than one port. A data stream flows in from certain ports, and flows out of other ports after being processed or buffered through a network device. Suppose that the data stream flows in from port A, and flows out of port B. This case may occur: When the rate of the data stream from port A is greater than the rate of the data stream out of port B, the buffer room in the device diminishes gradually. If this case continues for a sufficient time, the buffer inside the device overflows, and the data packets are hence lost. The duration depends on the size of the buffer inside the device, and the ratio of the inbound rate at port A to the outbound rate at port B. The greater the buffer is, the longer time it will take for the buffer to overflow; the greater the ratio of the inbound rate at port A to the outbound rate at port B is, the shorter time it will take for the buffer to overflow. The foregoing case can be prevented by limiting the inbound rate of the data stream at port A.
FIG. 2 shows how an ONT with n Ethernet ports processes the upstream Ethernet packets to the OLT in a GPON system. The Ethernet packets “E1” and “E2” from a customer premises equipment (CPE) 1 are converged with the Ethernet packet “E3” from a CPE n by a medium access control (MAC) bridge module 21 of the ONT, and sent to a GPON protocol processing module 22 through an internal Ethernet port. The GPON protocol processing module 22 adds the corresponding GPON protocol packet header information Px, Py, and Pz into the packets and then sends the packets to the OLT in the allocated timeslots. When the sum of the rates of data streams received by the MAC bridge module 21 of the ONT from all the UNIs is greater than the total upstream bandwidth of the ONT allocated by the OLT, it is necessary to perform traffic control for the data streams on the ONT to prevent overflow of the internal receiving buffer of the ONT. Moreover, when multiple users share an ONT and each user occupies an Ethernet port of the ONT, if a user supports sending of traffic greater than the traffic of the bandwidth allocated by the OLT to the ONT, congestion will occur in the MAC bridge module 21 of the ONT, and the ONT will discard the packets beyond the allocated bandwidth. Consequently, the denial of service (DoS) attack occurs, and affects normal services of other users.
A traffic descriptor ME is defined in the BPON and GPON standards. The GPON encapsulation method (GEM) traffic descriptor ME monitors the upstream traffic identified by the GEM Port-ID. This ME is associated with the GEM port network connection termination point (CTP) ME. This ME is described below:
ME: GEM traffic descriptor.
Data relationship: This ME is associated with a GEM port network CTP ME. The features of the upstream traffic identified by the GEM Port-ID are expressed by this ME.
The attributes of this ME are shown in Table 1
TABLE 1ME IDThis attribute provides a unique ID for each instanceof the ME. (mandatory, 2 bytes)SIRThis attribute represents the sustained informationrate (SIR), measured in byte/s. (optional, 4 bytes)PIRThis attribute represents the peak information rate(PIR), measured in byte/s. (optional, 4 bytes)
In the GPON standard, the GEM traffic descriptor ME is associated with the GEM port network CTP, both being used to configure and manage the corresponding attributes in the GPON protocol processing module in the ONT. The GEM port network CTP configures and manages a GEM Port. Therefore, when a data stream passes through this GEM port, traffic control will be performed according to the GEM traffic descriptor.
In the prior art, the traffic control is performed only at the GEM port network CTP. As shown in FIG. 2, when the sum of the rates of data received by multiple UNIs is greater than the rate of data transmitted from the MAC bridge module to the GPON protocol processing module through an internal Ethernet port, a traffic conflict occurs on the MAC bridge module. Suppose that the rate of a data stream received by UNI 1 is high but the data significance is low, while the rate of another data stream received by UNI n is low but the data significance is high. The low-significance and high-rate data stream at UNI 1 may lead to loss of the high-significance and low-rate data stream at UNI n.